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INA236: Current measurement using INA236

Kazuki Kuramochi
Genius 9455 points
Part Number: INA236

Hello Expert,

My customer evaluating INA236 but they have trouble reading acquiring data from Current register.
Then, Would you answer following questions?

  1. Current register is calculating current from voltage on shunt register(Vshunt/Rs).
    Is this understanding correct?
  2. They confirmed current register value when they using this device with following setting.
    However, register value is approx.~10 times against  actual value.
    Is there any miss understanding?
    Condition:
    ADCRANG=0(81.93mV)
    Rs=5mohm
    Maximum current=10A
  3. Would you provide formula to calculate following value?
    SHUNT_CAL=3555.4432(dec)=>D1B(Configured value)
    CUrrent_LSB=0.000A/LSB(dec)=>?(Configured value)
    SHUNT_CAL=0.050ohm(dec)=>?(Configured value)
    SHUNT_CAL=10.00A(dec)=>?(Configured value)
  4. Shunt voltage register is the value of after the internal amp?(On the other hands, does this value included amp's offset and gain variation?)

I'm looking forward to hearing back from you.

Best regads,
Kazuki Kuramochi

  • 0
    TI__Expert 4720 points

    Hello,

    1, Yes with the value of the SHUNT_CAL.

    2, I do not understand the question maybe it can be answered in question 3. Moreover the device in this configuration should have a max current above the 10A so you should be fine to measure 10A.

    3, You will need to first calculate Current_LSB = max current/(2^15) = 10/(2^15) = 0.00030517578125. Then we calculate SHUNT_CAL = .00512/(Current_LSB*Rshunt) = .00512/(0.00030517578125*.005) = 3355.4432 or decimal 3355. This value should be programmed into the SHUNT_CAL and then try to read the current register. 

    4, The shunt voltage is sensed at the input of the device, then can be read on the shunt voltage register. This value will have errors associated with it which are described in the datasheet. 

    If you have anymore questions please reply

    Regards,

    Castrense

  • 0 in reply to Castrense Nigrelli
    TI__Genius 9455 points

    Hello Castrense,

    Thank you for your swift reply.
    I understand you resolved my questions.

    I'll contact you when we get new question.


    Thank you and best regards,
    Kazuki Kuramochi

  • 0 in reply to Kazuki Kuramochi
    TI__Expert 4720 points

    Hello Kazuki Kuramochi,

    You are welcome. If you have any further questions you can reply to this thread.

    Regards,

    Castrense